Support for import/export at runtime

[verenkoska]

Support for import/export at runtime

[tmikov]

The Hermes parser supports the syntax, but the Hermes runtime does not currently have a supported implementation of ESM (ES6 modules).

The main reason is that React Native relies on bundler (usually Metro) which provides its own non-standard implementation of ESM, with various customizations, so the Hermes implementation would not even be used.

This is unfortunate, because built-in support of ESM provides opportunities for a number of important optimizations (like inter-module inlining). Static Hermes will eventually provide ESM, but as of now it still doesn't either.

[verenkoska]

Thanks for the fast response @tmikov ! This is unfortunate
And what about commonjs syntax? It also seems to work with -commonjs flag but not when using JSI

[tmikov]

JSI is an API to access the VM at runtime, it is orthogonal to this. Hermes does ship with a runtime implementation of commonjs, but it is unsupported and we don't recommend using it.